Crash/Near-Crash Analysis of Naturalistic Driving Data Using Association Rule Mining

Table 2

Description of the categorical variables and their attributes.

	Variable	Attribute	Description/definition
Severity	Event severity	Crash	The outcome of event, only considering the crash event and near-crash event
		Near crash
	Crash severity	I—most severe	The ranking of crash severity. This variable is coded only for events that include a crash
		II—police-reportable crash
		III—minor crash
		IV—low-risk tire strike
Road	Traffic flow	Divided (median strip or barrier)	The roadway design
		No lanes
		Not divided
		One-way traffic
	Travel lanes		The number of lanes
		Alignment		Curve	Roadway alignment
	Straight
	Road grade	Nonlevel	Roadway grade
		Level
	Driver	Driver behavior	Yes	Whether improper behaviors such as aggressive driving appear or not
No
Driver impairments		Yes	Whether any apparent impairments such as intoxication or fatigue appear or not
		No
Secondary task		Secondary task observed	Whether the driver engages in any secondary tasks or not
		No secondary task observed
Age group		16-19	The age group of drivers
		20-24
		25-34
		35-64
		65-99
Gender		M	Gender of drivers
		F
Annual miles		Less than 10,000 miles	Estimated average annual mileage over five years
		10,000-15,000 miles
		More than 15,000 miles
NUMVIOL		0	The number of moving or traffic violations the participant has had in the three years
		1
		2 or more
NUMcrash		0	The number of crashes the participant has been involved in during the three years
		1
		2 or more
Score full text		1—perfect	The clock drawing performed by the participant was scored based on a six-point scoring system
		2—minor visuospatial errors
		3—inaccurate time, minor visuospatial errors
		4—moderate visuospatial errors
Environment	Traffic density	Free flow	The density of traffic flow
		Stable flow
		Unstable/forced flow
	Intersections entered	Yes	Whether interrupted by controlled intersections or not
		No
	Traffic control	Yes	Whether influenced by any traffic controls or not
		No
	Surprised	Yes	Whether anything might be considered surprising to an average driver or to this particular driver occurs or not
		No
	Locality	Residential	The surrounding area
		Business/industrial
		Others